There are several types of prior art dispensing systems used for dispensing metered amounts of liquid or paste for a variety of applications. One such application is in the assembly of printed circuit boards and integrated circuit chips. In this application, dispensing systems are used in the process of encapsulating integrated circuits with an encapsulating material and in the process of underfilling flip integrated circuit chips with an encapsulent. Prior art dispensing systems are also used for dispensing dots or balls of liquid epoxy or solder onto circuit boards and integrated circuits. The liquid epoxy and solder is used to connect components to a circuit board or to an integrated circuit. The dispensing systems described above include those manufactured and distributed by Camelot Systems, Inc., the assignee of the present invention, under the name CAM/ALOT.RTM..
The dispensing systems described above are typically used in an electronics manufacturing facility in an automated assembly line with other equipment used in a circuit board or integrated circuit manufacturing process. The other equipment in-line with the dispensing systems may include, for example, pick and place machines, which place components on circuit boards, or reflow ovens that are used to cure materials dispensed onto the circuit boards or integrated circuits.
In a typical dispensing system, a pump and dispenser assembly is mounted to a moving assembly for moving the pump and dispenser assembly along three mutually orthogonal axes (x, y, z) using servomotors controlled by a computer system or controller. To dispense a dot of liquid on a circuit board at a desired location, the pump and dispenser assembly is moved along the horizontal x and y axes until it is located over the desired location. The pump and dispenser assembly is then lowered along the vertical z axis until the nozzle of the pump and dispenser assembly is at an appropriate dispensing height over the board. The pump and dispenser assembly dispenses a dot of liquid, is then raised along the z axis, moved along the x and y axes to a new location, and is lowered along the z axis to dispense the next liquid dot.
During the manufacture of circuit boards, it is sometimes necessary, or desirable, to dispense two different liquids or pastes onto a circuit board or to dispense different volumes of the same material. Dispensing systems have been designed that can dispense one of a number of dispensing materials from one dispensing head. One example of such a dispensing system is described in U.S. Pat. No. 5,795,390, filed Aug. 24, 1995, which is incorporated herein by reference. However, these dispensing systems typically are only able to dispense one material at a time, and the throughput of product in these systems may be less than desired because of the time required to dispense multiple materials serially using one dispensing head.
To overcome the throughput problem, two dispensing systems may be placed adjacent to each other with the first dispensing system dispensing one material and the second dispensing system dispensing a second material. This solution is expensive since two complete machines are used, and since additional manufacturing space is required. In typical operations, manufacturing floor space is limited, and it is desirable to limit the "footprint" of each manufacturing system on the manufacturing floor.
In electronics assembly, it is not uncommon for some manufacturing systems to utilize multiple conveyor systems operating in parallel to increase product throughput of the systems. Typical prior art dispensing systems do not include multiple conveyor systems and are not fully compatible with other in-line systems using multiple conveyors. Therefore, it would be desirable to provide a dispensing system having multiple conveyors.